Fuel cells have been proposed as a power source for electric vehicles and other applications. In proton exchange membrane (PEM) type fuel cells, hydrogen is supplied as a fuel to an anode of the fuel cell and oxygen is supplied as an oxidant to a cathode of the fuel cell. A plurality of fuel cells is stacked together in fuel cell stacks to form a fuel cell system. The fuel is typically stored in hollow pressure vessels, such as fuel tanks, disposed on an undercarriage of the vehicle.
The pressure vessels are typically multi-layered and include at least an inner shell and an outer shell. The inner shell may be manufactured using a variety of known methods including: machining; roll forming; injection molding; extrusion blow molding; blow molding; rotational molding; and the like. The inner shell is formed utilizing the rotational molding method by disposing at least one boss in a die cavity with a polymer resin, heating the mold while it is rotated causing the resin to melt and coat walls of the die cavity, cooling the die, and removing the molded inner shell. The finished inner shell is fixed to the at least one boss at an end thereof. To form the outer shell, the molded inner shell typically undergoes a filament winding process. After the filament winding process, the outer shell may require a significant amount of curing time prior to an initial pressurization of the pressure vessel.
A curing time of the pressure vessel may be decreased by exposing an exterior surface of the pressure vessel to elevated temperatures. The elevated temperatures during curing may undesirably increase the ductility of the inner shell. Accordingly, the curing temperature may be limited, especially the curing temperature to which the interior cavity is exposed. The curing time also increases a cost of manufacture of the pressure vessel. Some portions of the pressure vessel may require additional winding, resulting in a portion of the outer shell having a greater thickness than a remaining portion. As a result, the curing time for the greater thickness in the portion of the outer shell is increased.
Severe variations in a temperature of the inner shell may limit a transfer rate of fuel to and from the pressure vessel. Accordingly, a control system may regulate the transfer rate to and from the pressure vessel to militate against severe variations in a temperature of the pressure vessel.
The pressure vessel may be considered “full” during the pressurization when the contents of the pressure vessel reach a particular density. As the temperature within the pressure vessel increases during pressurization, the amount of pressure needed for the contents to reach the particular density also increases. Consequently, excessive amounts of energy may be expended to pressurize the pressure vessel until the contents reach the particular density when the temperature within the pressure vessel is increased.
The presence of the outer shell may undesirably increase a refueling time of the pressure vessel. As hydrogen or other fuel is transferred to an interior cavity of the pressure vessel at pressures up to 12,690 psi (875 bar), a temperature within the pressure vessel increases. The outer shell, typically formed from a material that conducts heat poorly, insulates the inner shell. As a result, the transfer rate of fuel to the interior cavity may be limited, increasing the refueling time of the pressure vessel.
The presence of the outer shell may undesirably decrease a transfer rate of fuel from the pressure vessel. As hydrogen or other fuel is rapidly removed from the interior cavity of the pressure vessel, a temperature within the pressure vessel decreases. The outer shell, typically formed from a material that conducts heat poorly, insulates the inner shell. The outer shell militates against the fuel within the pressure vessel from absorbing energy from an ambient environment. As a result, the outer shell may limit the transfer rate of fuel from the interior cavity.
It would be desirable to develop a pressure vessel having an outer shell, an inner shell, and a temperature regulating device, the temperature regulating device adapted to regulate the temperature of the inner shell during operation of the pressure vessel and to decrease curing time during manufacture of the pressure vessel.